I think I'm starting to get the balance of the new faction system right. I've been playing an extremely interesting game with the current development version (1.32.17) starting as the Count of Korinthos in 1066.
~100 years in, I'm King of Serbia (thanks to a lucky marriage) and control the Duchies of Achaia and Adrianopolis in Hellas. My son and heir is Duke of Sicily.
My liege took the throne at age eight and started off by poking out the eyes of the six year old Duchess of Sicily (later my wife, currently deceased by suicide). I joined a general rising against her, and was winning the decisive battle when my character died in battle, causing my loyalist brother (the sad sack of a naive appeaser above) to inherit and my armies
to switch sides in the middle of the battle. She's since beat down several more attempts to depose her, and has even fought off a Jihad (though mostly because Rum was busy fighting over some levantine province and did not participate).
Speaking of Rum, the Seljuks won the initial war and then won a Jihad for Nicaea, resulting in the fairly terrifying Rum-Persia-Mesopotamia-Azerbaijan you see here. If they hadn't been busy during the last Jihad they would hold Constantinople right now.
Last decade was some kind of Separatist world revolution. The HRE lost Bohemia, Bavaria and bits of Italy and Lotharingia, France was reduced to a rump state and the Fatimids shed most of their territory outside of Egypt. Kiev collapsed early in the game and has since ceased to exist.